Shear strengthening of reinforced concrete beam using natural fibre reinforced polymer laminates

Abstract

Shear strengthening of reinforced concrete beam using externally bonded steel plate and carbon fibre reinforced polymer laminate (CFRP) is the common practices in construction industry. However, high expense of CFRP laminate and corrosion of steel plate are the drawbacks of those materials. Thus, natural fibre based composite plate could be the alternative for shear strengthening of reinforced concrete structure. The aim of this research work was to develop high strength natural fibre based composite plates for the possible application in shear strengthening of reinforced concrete structure. In the experimental programme, the plates were fabricated using kenaf, jute and jute rope fibres in treated and untreated conditions. A total of eight beam specimens were prepared to investigate the structural behaviour, the beams were shear strengthened using treated and untreated natural fibre composite plates and CFRP laminates including control beam. Embedded connectors were used to eliminate debonding failure of the laminates. The shear strengthened beams with untreated kenaf, jute and jute rope composite plates had shown 35%, 36% and 34% higher failure loads as compared to control beam respectively. The structural behaviour of strengthened beams with treated composite plates was found to be comparable with those of untreated. Beam with jute rope composite plates showed lower failure load as compared to those of fibres due to fracture of plate followed by shear failure. Strengthened beams with natural fibres composite plates had shown higher ductility and higher failure loads as compared to those of CFRP laminates. The failure load, ductility, crack patterns and strain characteristics of strengthened beams with natural fibre composite laminates were found to be closely comparable with CFRP laminate strengthened beam.